Purpose: Bone scintigraphy is a diagnostic study used to evaluate the distribution of active bone formation in the body. 

Patient Preparation:

1. No fasting is required.

2. Explain the procedure to patient.

3. Unless contraindicated, patients should be well hydrated and instructed to drink 1.5 to 2 liters or around 8-oz glasses of water between the time of injection and the time of delayed imaging.

4. Patient is encouraged to empty urinary bladder more frequently.

5. Give strict instructions to avoid urine contamination of clothing.

6. The patient should be asked to urinate immediately before delayed imaging and to drink plenty of fluids for at least 24 h after injection.  

Patient information and precautions:

1. Ask about any history of fractures, trauma, osteomyelitis, cellulitis, edema, arthritis, neoplasms, metabolic bone disease, or limitation of joint movement.

2. Enquire about current symptoms.

3. Ask if any previous bone scan done or any other recent scintigraphy, (especially with 131I,  67Ga).

4. Any recent CT /MRI / X- Ray reports and scan films.

5. Relevant laboratory results (e.g., prostate-specific antigen in patients with prostate cancer)

6. In females of reproductive age enquire if pregnant or breast-feeding. Pregnancy is a contraindication, unless terminally ill or warranted by referring doctor, for a bone scan. Doubtful cases of pregnancy have to be confirmed before injecting the MDP dose for medico legal purposes.

7.      History of therapy that might affect the results of bone scintigraphy (e.g., antibiotics, steroids, chemotherapy, radiation therapy, diphosphonates, or iron therapy)

8.      History of orthopedic and nonorthopedic surgery to see for prosthetic implants , colostomy bag , that might affect the results of bone scintigraphy

9. History of any known anatomic or functional renal abnormalities. Check if patient has an indwelling catheter /condom drainage for urine and ensure there is no urine leak from the drainage site.  

PROTOCOL:

Depending on the indication or purpose of the study you must decide whether three phase or static skeletal phase images are required.

1.Dynamic study  (2-5 seconds per frame): shows the vascularity of region of interest.

2.Blood pool image (500K counts): done 5 min post injection. 

3.Planar bone scan (Static Skeletal phase images) 

4.SPECT bone scan:  produces a tomographic image of a portion of the skeleton. 

The blood flow images are a dynamic sequence of planar images of the area of greatest interest obtained immediately after the tracer is injected.

The immediate (blood pool or soft tissue phase) images include 1 or more static planar images of the areas of interest, obtained immediately after the flow portion of the study and completed within 5-10 min after injection of the tracer.

Delayed skeletal phase images acquired 3 – 4 hours post inj. and may be

1. Limited to the areas of interest i.e. regional bone scan

2. May include the whole body (anterior and posterior projections) or spot views of entire skeleton,

3. May be tomographic (SPECT),

4. If necessary, additional delayed images may be obtained up to 24 h after tracer injection known as 4-phase bone scan.      

Procedure:

In most of the institutions, the imaging sequence for a patient without a history or suspicion of malignancy who complain of back, hip, knee or temporomandibular joint pain is as follows:  

1.Dynamic study

2.Blood pool study

3.Planar static images

4.SPECT scan.  

If doctor is not around better do all first three phases.  

Doctor will decide if SPECT is required.  

SPECT supplements but does not replace planar imaging. Patients referred for the evaluation of osteomyelitis, orthopedic problems or Sports injuries require bone scans that are carefully tailored to their individual requirements.

Osteomyelitis case needs three phase bone scan. Evaluation of orthopedic disorders and sports injuries usually calls for planar bone scans which show best possible anatomical

Details. This requires high-resolution collimation and may call for special positioning, such as oblique views of the shoulder or plantar views of the feet.

Even when optimal high-resolution planar images are acquired, in addition SPECT images frequently yield additional valuable diagnostic information.

For oncology patients most of the institutions prefer to obtain a whole body sweep if there is a dual head gamma camera or multiple overlapping bone scan images in single head system. When only spot views are to be acquired take care not to miss any regions of the skeleton.

Once the whole body sweep or spot images are acquired, check if any extra views will be required before removing the patient from the table. 

Multiple static images have higher resolution than whole body scanning images. 

The superior resolution of spot images aids detection of bone metastases and facilitates accurate anatomical localization of skeletal lesions. 

Protocols for planar bone scans : 

Adult dose: 740Mbq (20 mCi).  If obese give more dose upto 30mCi 

Children dose: Infants 1mCi enough.  Others anywhere between 3 - 8mCi                    depending upon age and body weight. Recommended 9–11 MBq / kg (250–300 µCi /kg), with a minimum of 20–40 MBq (.5–1.0 mCi) 

IV injection:      Do not extravasate

                        Preferably give injection in a new vein

                        Better to avoid established IV lines.  

Patient Positioning:

This is very important especially for bone scan. Patient should be positioned supine, exactly at the center of the table with no pelvic tilts. While using whole body sweep take care to tuck the dress correctly otherwise the distance from detector will vary.  

• Encourage oral fluids and frequent voiding.
• If patients can’t drink or if it is contraindicated start IV fluids. 500-1000ml dextrose saline or saline.
• Remove metal objects like belts, coins from pocket, pen etc and ask patient to void before scan. Remove any breast cushions, metallic implants if any, in patients with Breast cancer prior to scan.
• Inj site: Remove the cotton swab from the injected site while positioning the patient for the scan as it maybe contaminated. Place the hand out of the field of view, otherwise bones will not be well visualized.
• Ask if patient is having any prosthesis.
• If undergarments are heavily contaminated  - Remove.
• Any other cloth contaminated – remove, give a gown or lungi
• Infants  - change the diaper before scan, many times other clothes

                 also may have to be changed.

Image acquisition parameters: Scanning 3-4 hours after injection. 

1.Whole body technique: 10 min/meter (12-15 cm/min.) adequate. Auto contour option if present can be used. 

2.Multiple overlapping bone scan views or a whole body sweep depending on camera type and physician preference.

Collimators: Low energy high resolution or high-resolution parallel hole collimation according to doctor’s choice and collimator availability.

Acquisition time and matrix:  Spot images may be obtained using a 128 ´ 128 ´ 16 or 256 ´ 256 ´ 16 matrix. Whole-body views are usually obtained in a 256 ´ 1024 ´ 16 or greater matrix. Acquire 500k-1000k thoracic spine scan Note the time Obtain all other spots for the same duration.

For Flow and soft tissue phases: Camera should be positioned over the region of interest before tracer injection. The acquisition computer should be programmed to acquire approximately 30 frames. When digital images are acquired, blood flow images may be obtained in a 64 ´ 64 ´ 16 or greater matrix at 1–3 s/frame. If film is used, 3–5 s/frame may be used.

Blood pool (tissue phase) images should be acquired immediately after the flow portion of the study for approximately 3–5 min/image in a 128 ´ 128 ´ 16 or greater matrix, with count density of approximately 300,000 counts/image (150,000–200,000 counts/image may be adequate for extremities).

Other views (e.g., lateral, oblique, or tangential) and special views (e.g., frog-leg views

of the hips or sitting-on-detector [caudal] views of the pelvis) may be obtained when
necessary. 

Renal failure patients:  Inject first and schedule their scan – last. Waiting for > 5 hours may be required for optimum quality scan in these patients due to poor renal clearance of unbound tracer. 

Children and infants: 

Technically demanding for imaging children. Most of the children cooperate. Befriend them, talk, and offer chocolates, teddy bears. For infants do not use couch place them directly on detector. Immobilisers may be required like velcro fasteners are sufficient. Oral sedation with syrup Trichlofos is useful in age group of less than 1 year, dose 25 mg/kg body wt, for older children 400-500 mg is given 30- 45 min prior to scan. In extremely uncooperative children Inj. Ketamine or midazolam  may be required.  

Planar Bone scanning pitfalls

                Pitfall                                                             Result  

1.Over 5cm collimator to patient                     Resolution loss

    separation 

2. Wrong energy windows                              Resolution loss

3. 99mTc-MDP impurities                                  Increased background

                                                                            & soft tissue uptake

4. Renal failure                                                    Increased background

5. Slight patient motion                                     Resolution loss

6. Obesity                                                  Increased background & scattered activity 

Protocols for SPECT bone scan

1.Adult dose: 25mci 

2.Acquisition  3-4 hours later , 64 X 64 matrix 

3.General method: LEAP or LEGP collimator is used.20seconds/projection, 64 projections over 360 degrees.

4. High resolution method (option for lumbar spine): LEHR ,25-30 seconds/projection,64 projections over 360 degrees  

Processing 

• Uniformity correction
• Hanning filter (frequency cutoff = 0.8 cycles/cm pre-processing)
• Reconstruct by filtered back projection with Ramp filter
• No attenuation correction
• 6mm (one pixel) thick transaxial, sagittal & coronal images

Display

• Use linear gray scale map for TMJ, Lumbar spine & knee SPECT
  
• Use log gray scale when searching for femoral head AVN.  

Special patient positioning for SPECT bone scanning  

Bony structure               Special position                           Comments 

Knees                 5-7.5cm pad between knees              for obese pts both knees may

                           secure knees with straps.                   not fit in field.

                           Secure feet in neutral position          to prevent rotation.

Hips and                  Empty bladder                             Bladder filling will create artifact

Pelvis                   Position hips symmetrically             

                             Secure knees and feet to prevent          motion

Lumbar spine       Keep arms out of fields                     as  pts in pain may move

                             Pillow under knees may relieve         back pain  

TMJ                      Secure neck in comfortable               check lateral view to be

                             hyperextension ,                                 sure that chin is in the

                             Instruct patient not to talk                   field of view. 

Unique acquisition problems and how to solve  

1.Patient unable to empty the bladder . We cannot image the pelvic bony structures.
Use a lead pot over the bladder and acquire for a longer duration than usual. Posterior pelvic view acquire one image with a lead  pot over the bladder position and another without a lead pot. 

2.End on view or TOD views to separate bladder from pelvic bones. 

3.Attenuation from the couch : Do not acquire posterior views through the couch. After anterior view ask patient to lie down in prone position. Even if patient cannot lie down in prone position do posterior views in sitting or standing position.

4. Humeral head  : Best viewed in posterior oblique images 

5. Femoral head  : Pin hole  or SPECT 

6. Small bones and joints of feet and hand : place directly on detector. 

7. When imaging hand or feet which are positioned on detector use a radioactive marker.  

8.Hot spot in 11th or 12 th rib : differentiate from kidney activity by taking oblique views.

9. Lesions in tibia  : take lateral views / dancing position

Interpretation:

Homogenous tracer distribution should be seen in all the bones in a normal patient. Any focal area of increased uptake i.e. Hotspot is abnormal. Similarly cold defects are also abnormal provided it is not due to any artifact. 

Normal bone scan appearance in a child shows prominent uptake in growing ends of bones i.e. in epiphyses.

Effect of distance from the collimator, as the distance from collimator increases resolution worsens

Pattern recognition: hot spot in the mandible may be due to dental disease. Please enquire. When one kidney is not found try to locate it. In this case one can overlook this and report it as metastasis

Hard copy of Image: Very important for bone scans as correct contrast has to be applied, if overexposed cannot see the details. Manipulate the contrast in such a way that details of the pathology are seen well. 

When patient is scheduled for both I 131 scan and Bone scan, preferably do bone scan first and then administer I-131. Sufficient time gap between two scans is necessary.